Shim Pipeline Specification for the Unheaded Protocol Computer

This document specifies the Shim pipeline for the Unheaded Protocol Computer (UPC). The Shim translates MBC (Monad Bytecode) programs into eBPF execution contexts, defines the per-hop processing model, and specifies the tick packet protocol that drives distributed computation across IPv6 network hops. The pipeline implements a four-stage architecture: Assembly, Verification, Loading, and Execution, with integrated support for memory-mapped I/O, framebuffer rendering, and CRC validation.